Yun Heum Park

Spectrum defects such as hot band and rainbow spectra on back light unit (BLU) composed of prism film and diffusing film have been examined by optical analysis. Hot band and rainbow phenomenon could be resulted from rapid luminance decrease and fluctuation in spectra at viewing angles in the range of 30–40° and 50–70°, respectively. By optical simulation with modification in prismatic structure, it is suggested that spectrum defects could be diminished or eliminated in both calculated simulation and practical prism pattern when the plane structure of prism is changed from straight to slow curved.

Electroactive graft copolymers with different length and number of branches, poly(vinyl carboxy ethyl ether)-g-poly(pyrrole)s [PVCEE-g-(PPy)s] were able to be prepared according to the following steps; PVCEE was synthesized by reacting poly vinyl alcohol (PVA) with 3-chlolopropionic acid (CPA). Poly(vinyl pyrrolyl propanone ether) (PVPPE) was synthesized by fully or partially substituting carboxyl groups of PVCEE via carbonyl chloride groups with carbonyl pyrrolyl groups. Fully or partially substituted pyrrolyl groups in PVPPE act as the nuclei for electrochemical polymerization of pyrrole. Electroactive graft copolymers with different number of branches and length of pyrrolyl groups were finally obtained by keeping the total number of repeating groups of all branches constant on electrochemical polymerization of pyrrole on pyrrolyl groups of PVPPE. The differences of electrochemical properties and electroconductivity of these PVCEE-g-(PPy)s were investigated using cyclic voltammetry (CV) and chronoamperometry (CA). Synthesis of PVCEE-g-(PPy)s was characterized using FT-IR spectroscopy and ¹H-NMR.

A novel conducting graft copolymer (PVCEE-g-PPy) of poly(vinyl carboxy ethyl ether) (PVCEE) and polypyrrole (PPy) was prepared by electrochemical polymerization of pyrrole using a precursor, poly(vinyl pyrrolyl propanone ether) (PVPPE). For synthesis of the graft copolymer, PVCEE was first synthesized by reacting poly(vinyl alcohol) with 3-chloro propionic acid. The precursor PVPPE for PVCEE-g-PPy was then synthesized from PVCEE. The chemical structures of PVCEE and PVPPE were confirmed by FT-IR spectroscopy and ¹H-NMR. Electrochemical properties of the novel conducting graft copolymer were compared with those of the PVCEE/PPy composite using cyclic voltammetry (CV) and chronoamperometry (CA). It was confirmed that the pyrrolyl group of the precursor polymer can act as the nuclei for the graft polymerization of pyrrole into PVPPE.

The spherical poly(methylsilsesquioxane) (PMSQ) beads with the diameter of 2, 5 and 10 micron, respectively were prepared from methyltrimethoxysilane (MTMS) by two steps, acid hydrolysis and base condensation process in aqueous solution. Acetic acid and ammonium hydroxide were used to initiate the acid hydrolysis and base condensation, respectively. The bead size was affected and controlled by the reaction variables, such as the agitation speed, reaction temperature, solvent and concentration of monomer and catalyst. The prepared PMSQ beads were characterized by ²⁹Si CP/MAS NMR and FT-IR. Especially in preparing the spherical PMSQ bead with the diameter of 10 micron, it was found that organic solvent was necessary to obtain the desired size compared with the preparation condition of 2 and 5 micron beads. The prepared PMSQ beads showed good thermal stability and compression recovery ratio. The haze value of PMSQ beads was remarkably higher than that of acrylic beads due to the relatively low refractive index of PMSQ.

The novel photopolymers having photoreactive pendant group were designed and synthesized through the reaction between precursor, poly(methacrylic acid-co-2-hydroxyethyl methacrylate-co-styrene)(poly(MAA-HEMA-STY)) and photoreactive compounds such as methacryloyl chloride (MAC), cinnamoyl chloride (CC), methacryloyl isocyante (MAI) and 3-isopropenyl-α, α-dimethylbenzyl isocyanate (TMI), respectively. The prepared poly(MAA-HEMA-STY) and novel photopolymers were characterized by ¹H-NMR and FT-IR spectroscopy. The photosensitivity of photopolymers was estimated with the UV exposing time by FT-IR spectra change at 1630 cm⁻¹. The photosensitivity of photoresists was determined by calculating the UV energy at the pattern-remaining step after developing the thin film using gray-scale mask. In connection with the photosensitivity the surface hardness and compression properties of photopolymer films were determined by nano indenter. All prepared photopolymers revealed higher surface hardness than poly(MAA-HEMA-STY). Photopolymers with methacryloyl functional side group showed better photosensitivity than photopolymers with vinyl aromatic and cinnamoyl group. Especially photopolymer prepared from poly(MAA-HEMA-STY) and MAI showed good potential for the application of negative-working photoresist.

The electrically conductive graft (g) copolymer, poly(dimethylolpropionic acid –co-adipoyl chloride)-g-poly(aniline) (PDMPAAC-g-PAni) was prepared by the electrochemical polymerization of aniline (Ani) using a precursor polymer, poly[(4-aminophenyl)-dimethylolpropionic amide-co-adipoyl chloride] (PADMPAAC). PADMPAAC was synthesized chemically by reacting PDMPAAC with 1,4-phenylenediamine. The electrochemical properties of graft copolymer are compared with those of PDMPAAC/PAni composites. Synthesis of PDMPAAC and PADMPAAC was characterized using ¹ et al. , ( 1997 ). Handbook of Organic Conductive Molecules and Polymers , John Wiley & Sons Inc. : Chichester . [Google Scholar] H-NMR, FT-IR spectroscopy. The electrochemical properties of the novel conducting copolymer were investigated using cyclic voltammetry (CV) and chronoamperometry (CA); thermal properties were investigated using thermogravimetric analysis (TGA). The electric conductivity was measured with four-probe method.

In order to study the effect of glass transition temperature (T_g) on the compression and elastic recovery properties of polymer, several poly(meth)acrylate copolymers having three or four segment units composed of methacrylic acid (MAA) and other vinyl monomers such as glycidyl methacrylate (GMA), styrene (STY), butyl acrylate (BAM), 2-hydroxyethyl methacrylate (HEMA), methyl methacrylate (MMA), benzyl methacrylate (BzMA), 2-ethylhexyl acrylate (EHA), octadecyl acrylate (ODA), ethyl acrylate (EAM), and lauryl methacrylate(LMA) were synthesized. The synthesized copolymers showed different glass transition temperatures depending on the component type. Thin films and micro patterns were prepared by photolithography process (spin coating/pre-baking/UV-exposure/KOH developing/post-baking) with prepared copolymer solution. The compression and recovery property of copolymer films and micro patterns were determined by nano indenter. As a result, copolymers with lower T_g especially MAA/GMA/STY, MAA/GMA/STY/BAM, and MAA/GMA/STY/HEMA copolymers showed higher compression and elastic recovery ratio.

Poly(vinyl phenylmethylamine) (PVPMA) and poly(vinyl benzlmethylyamine) (PVBMA) were chemically synthesized and PVPMA/polyaniline (PANI) and PVBMA/PANI composites were electrochemically prepared for the investigation of the effect of different bulky side groups of matrix polymers on the electrochemical properties of the polymer composites. The cyclic voltammertry, chronoamperomtry, and conductivity were investigated.

The synthesis and characterization of the photoresist polymer for using as spacer in LCD panel were investigated. The poly(methacrylate-co-styrene) (PMHS) and NCO-terminated prepolymer were synthesized using radical initiator and catalyst, respectively, and in-situ, the poly(urethane-(methacrylate-co-styrene)) (PMHSU) was prepared with the PMHS and NCO-terminated prepolymer. The PMHS and the PMHSU were characterized by FT-IR, ¹H-NMR and thermal properties were investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). After the films were prepared by the sequential processes of spin-coating propylene glycol monoethyl ether acetate solution containing PMHSU, multifunctional monomer, and photoinitiator, pre-baking, UV-exposing and post-baking, the compression recovery of the films was investigated by nano-indenter. The negative patterns of the PMHSU were obtained by developing.